A boiling water reactor nuclear fuel assembly (or “BWR fuel assembly”) generally comprises a bundle of fuel rods maintained laterally by spacer grids distributed along the bundle of fuel rods, at least one tubular water channel provided within the bundle of fuel rods for channeling a flow of coolant/moderator separately from the fuel rods and a tubular fuel channel encasing the bundle of fuel rods for channeling a flow of coolant/moderator between and about the fuel rods. Similarly, a water-water energetic reactor nuclear fuel assembly (or “VVER fuel assembly”) generally comprises a bundle of fuel rods maintained laterally by spacer grids distributed along the bundle of fuel rods, at least one water rod provided within the bundle of fuel rods for channeling a flow of coolant/moderator separately from the fuel rods and a tubular fuel channel encasing the bundle of fuel rods for channeling a flow of coolant/moderator between and about the fuel rods.
A spacer grid generally defines a lattice of cells for receiving fuel rods and comprises a peripheral band composed of peripheral strips and delimiting the peripheral contour of the spacer grid. It preferably comprises positioning means provided on the peripheral band for ensuring an adequate lateral positioning of the spacer grid inside the fuel channel for ensuring an adequate flow of coolant/moderator between and about the fuel rods, namely about the peripheral fuel rods located adjacent to the inner walls of the fuel channel.
US 2005/0246961, EP 0 709 0857 and U.S. Pat. No. 6,156,043 disclose spacer grids comprising a peripheral band provided with rigid tabs, lobs or stops protruding outwardly from the outer periphery of the peripheral band and formed in the peripheral band and/or assembled to the peripheral band.